1. Field of the Invention
The present invention relates to a semi-conductive memory and the manufacturing method of the same, more specifically, to a non-volatile memory and its manufacturing method.
2. Description of the Related Art
Since the non-volatile memory can store data without constant power supply, therefore nowadays it is a very remarkable memory. As the memory components are made smaller and smaller, a flash memory as shown in FIG. 1 has been developed recently.
With reference to FIG. 1, the flash memory comprises a substrate 100, word gates 110, word lines 120, buried bit lines 130, poly-silicon spacers 140 and oxide/nitride/oxide (ONO) layers (not shown). FIG. 2A to FIG. 2E illustrates a sectional view of the manufacturing flow along the II-II line section of the flash memory in FIG. 1.
With reference to FIG. 2A, first a plurality of poly-silicon layers 102 is formed on the substrate 100. These poly-silicon layers 102 will later be patterned into word gates 110 in FIG. 1.
Next, with reference to FIG. 2B, an ONO layer 104 is formed to cover the substrate 100 and the poly-silicon layer 102. Next, the ONO layer 104 is fully covered by another poly-silicon layer 106.
Next, with reference to FIG. 2C, the poly-silicon layer 106 is etched back, so that a plurality of silicon spacers 140 is formed on the sidewalls of poly-silicon layer 102. Then an ion implantation process 108 is performed upon the substrate 100, so that a lightly doped drain (LDD) area 112 is formed in the substrate 100.
Next, with reference to FIG. 2D, an oxide spacer 114 is formed on the surface of the poly-silicon spacers 140; then another ion implantation process 116 is performed upon the substrate 100, so that a doped area serving as buried bit lines 130 is formed in the substrate 100.
Next, with reference to FIG. 2E, fill the dielectric layer 118 into the spaces between the poly-silicon layers 102, then a plurality of word lines 120 interlacing with the buried bit lines 130 are formed over the substrate 100. Wherein, the word lines 120 are formed by forming a full poly-silicon layer over the substrate 100 first, then pattern the poly-silicon layer to form word lines; and after the word lines 120 are formed, keep etching the poly-silicon layer 102 underneath so as to form blocks of word gates 110.
However, since the poly-silicon layers 102 on the substrate 100 which are near the corner of the ONO layer 104 is hard to be removed, there are usually poly-silicon residues 150 remained along the edges of the ONO layer 104, as shown in FIG. 1 and FIG. 3 (i.e. the sectional view of the line section III-III of FIG. 1). This results in the connection between two word lines and memory failure.